During the filtering of oil in working engines, particularly lubricated internal combustion engines such as in motor vehicles, [and in hydraulic equipment and automatic transmissions] oxidation and sulphur acidification of the oil commonly occur either requiring more frequent oil and oil filter changes, or adversely affecting engine operation over time. For that reason, it is known to utilize thermoplastic polymers having additives--such as anti-oxidants--incorporated therein in order to extend the time between oil filter changes and/or adequately protect the engine. Examples of these techniques are shown in U.S. Pat. Nos. 4,066,559 and 4,144,166, the disclosures of which are hereby incorporated by reference herein.
According to the present invention, a particular material, and geometric configuration, are provided which optimize the ability of an oil filter to neutralize sulfur acidification and oxidation. The material utilized according to the invention may be incorporated in an oil filter in a particular manner so as to enhance its functionality. The product is simple and easy to manufacture utilizing conventional equipment and all the materials going into manufacture are readily commercially available.
According to one aspect of the present invention, an oil filter for engines, hydraulic equipment, or automatic transmissions is provided. The oil filter comprises the following elements: A casing having first and second ends, and defining an interior volume, and having an opening adjacent the second end thereof. A particle filtering material comprising loose fibers filling up the vast majority of the interior volume. A pad of interlocked fibers covering the opening adjacent the second end of the casing. A thermoplastic material which gradually dissolves in above ambient temperature oil, the material having oil oxidation and acidification arresting additives which are released into the oil over time as the material dissolves, the thermoplastic material disposed between the particle filtering material and the pad.
The casing is typically a metal or plastic casing having a circular cross section with a pair of disc-shaped end plates and a ribbed wall with openings in both end plates. The particle filtering material typically comprises conventional long-strand, natural unbleached cotton packing (loose, not interlocked) which is compressed hydraulically to a specific air density to prevent channeling, and to achieve maximum particle retention. The natural cotton will remove some sulfur, thereby helping in reducing acidification. The pad of interlocked fibers preferably comprises a one micron felt pad (that is, for filtering out particles in the one micron size range) having a thickness of about 1/32-1/8 inch (e.g. about 1/16 inch). A conventional spin-on type of casing may be provided for the filter, if desired.
High molecular weight polypropylene has been found superior for use as the thermoplastic material compared with polyester polycarbonates, polyallomer, polyethylene, and polysulfone. Particularly desirable, polypropylene comprises ethylene propylene with a specific gravity of about 0.9, a Shore D hardness of about 70, and a tensile strength (not counting additives) of about 3900 lb./in..sup.2 (e.g. 3940). The material is particularly desirable in the form of spaghetti-shaped strands having a thickness of about 0.0625-0.125 inches and a length greater than about 2 inches, or rice-shaped pellets having a thickness of about 0.0625-0.125 inches and a length of about 0.3-0.7 (e.g. about 0.5) inches.
The thermoplastic material with additives may comprise about 83-90% liquid ethylene propylene and about 10-17 weight % dispersing agent, lubricant, and detergent neutralizer. The detergent neutralizer may comprise both detergent neutralizing sulfonate and phenate. For example, the additives may comprise about 3-5% dispersing agent, about 1-1.5% organic phosphate lubricant, about 2.5-3.5% detergent neutralizing sulfonate, and about 4.5-5.5% detergent neutralizing phosphate.
According to another aspect of the present invention, a method of producing an oil filter is provided. The method comprises the steps of substantially, continuously and consecutively: (a) Mixing anti-oxidation and anti-acidification additives with liquid thermoplastic material to form a thermoplastic mixture. (b) Extruding the thermoplastic mixture from step (a) into spaghetti like strands having a thickness of about 0.0625-0.125 inches. (c) Cooling the strands. (d) Cutting the strands into discrete elements, and (e) Placing the discrete elements into an oil filter held in place to contact above ambient temperature oil to gradually dissolve to release the additives therefrom. Step (c) may be practiced utilizing a cooling trough, and step (d) utilizing a chopper which cuts the plastic strands into pellet form and empties them into bags. Rice-shaped pellets having a length of about 0.3-0.7 inches are preferred, although alternatively step (d) may be practiced to produce spaghetti-like discrete elements having lengths of over 2 inches.
According to yet another aspect of the invention, a plurality of rice-shaped pellets are provided. Each of the pellets has a thickness of about 0.0625-0.125 inches and a length of about 0.3-0.7 inches, and comprises about 83-90% ethylene propylene polypropylene with a specific gravity of about 0.9 and a Shore D hardness of about 70, and about 10-17% additives comprising a combination of dispersing agent, lubricant, and detergent neutralizer. The polypropylene dissolves in above-ambient temperature oil to release the additives therefrom.
It is the primary object of the present invention to provide for the effective construction of an oil filter which neutralizes sulphur acidification and oxidation. This and other objects of the invention will become clear from an inspection of a detailed description of the invention, and from the appended claims.